MYb(BH₄)₄ (M = K, Na) from laboratory X-ray powder data

Two new borohydrides, potassium ytterbium tetra­boro­hydride, KYb(BH₄)₄, and sodium ytterbium tetra­boro­hydride, NaYb(BH₄)₄, have been synthesized via mechano­chemical reactions in the solid state. The two compounds are iso­structural and both crystallize in the Cmcm space group in the structure reported previously for NaSc(BH₄)₄ and KY(BH₄)₄. This crystal structure is composed of isolated homoleptic [Yb(BH₄)₄]^- anions surrounded by M⁺ cations (M = Na, K). The packing of the M⁺ cations and [Yb(BH₄)₄]^- anions is a distorted variant of the hexa­gonal NiAs structure type, with M⁺ forming distorted trigonal prisms, i.e. M₆. Each second prism surrounds a [Yb(BH₄)₄]^- anion, while the [Yb(BH₄)₄]^- anions are arranged into deformed octa­hedra around the M⁺ cations.

Computing details

For both compounds, data collection: DIFFRACplus (Bruker, 2006); cell refinement: JANA2006 (Petříček et al., 2006); data reduction: DIFFRACplus (Bruker, 2006); program(s) used to solve structure: JANA2006 (Petříček et al., 2006); program(s) used to refine structure: JANA2006 (Petříček et al., 2006); molecular graphics: VESTA (Momma & Izumi, 2011); software used to prepare material for publication: publCIF (Westrip, 2010).

(I) Potassium ytterbium tetraborohydride

Crystal data

KYb(BH4)4	Z = 4
Mr = 271.5	F(000) = 80
Orthorhombic, Cmcm	Dx = 1.781 Mg m^−3
Hall symbol: -C 2c 2	Cu Kα radiation, λ = 1.5406, 1.54439 Å
a = 8.4341 (13) Å	µ = 19.98 mm^−1
b = 12.445 (2) Å	T = 293 K
c = 9.6449 (15) Å	green
V = 1012.4 (3) Å^3	cylinder, 18 × 0.3 mm

Data collection

Bruker D8 Discover diffractometer	Scan method: continuous
Specimen mounting: quartz capillary	2θmin = 10°, 2θmax = 110.009°, 2θstep = 0.02°
Data collection mode: transmission

Refinement

Rp = 0.005	23 restraints
Rwp = 0.007	7 constraints
Rexp = 0.006	All H-atom parameters refined
R(F) = 0.020	Weighting scheme based on measured s.u.'s w = 1/[σ^2(I) + 0.0016I^2]
4889 data points	(Δ/σ)max = 0.044
Profile function: pseudo-Voigt	Background function: 30 Legendre polynomials
71 parameters	Preferred orientation correction: none

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
K1	0	0	0.5	0.085 (3)*
Yb1	0.5	0.13129 (17)	0.75	0.0544 (10)*
B1	0.5	0.2416 (13)	0.9453 (18)	0.117 (9)*
H1	0.5	0.299 (3)	0.039 (4)	0.140 (11)*
H2	0.5	0.1541 (17)	0.984 (5)	0.140 (11)*
H3	0.61134 (15)	0.257 (3)	0.879 (2)	0.140 (11)*
B2	0.7189 (19)	0.0223 (13)	0.75	0.117 (9)*
H4	0.834 (5)	−0.028 (5)	0.75	0.140 (11)*
H5	0.750 (9)	0.1122 (19)	0.75	0.140 (11)*
H6	0.646 (3)	0.002 (4)	0.84734 (13)	0.140 (11)*

Geometric parameters (Å, º)

B1—H1^i	1.15 (4)	B2—H4	1.16 (5)
B1—H2	1.15 (3)	B2—H5	1.15 (3)
B1—H3	1.152 (16)	B2—H6	1.150 (19)
B1—H3^ii	1.152 (16)	B2—H6^iii	1.150 (19)
H1^i—B1—H2	108.45 (3)	H4—B2—H5	110 (5)
H1^i—B1—H3	110.11 (2)	H4—B2—H6	109 (3)
H1^i—B1—H3^ii	110.11 (2)	H4—B2—H6^iii	109 (3)
H2—B1—H3	110 (2)	H5—B2—H6	110 (3)
H2—B1—H3^ii	110 (2)	H5—B2—H6^iii	110 (3)
H3—B1—H3^ii	108.18 (3)	H6—B2—H6^iii	110.86 (3)

Symmetry codes: (i) x, y, z+1; (ii) −x+1, y, z; (iii) x, y, −z+3/2.

(II) Sodium ytterbium tetraborohydride

Crystal data

NaYb(BH4)4	Z = 4
Mr = 255.4	F(000) = 80
Orthorhombic, Cmcm	Dx = 1.840 Mg m^−3
Hall symbol: -C 2c 2	Cu Kα radiation, λ = 1.5406, 1.54439 Å
a = 8.438 (4) Å	µ = 18.37 mm^−1
b = 12.057 (6) Å	T = 293 K
c = 9.057 (4) Å	green
V = 921.5 (7) Å^3	cylinder, 18 × 0.3 mm

Data collection

Bruker D8 Discover diffractometer	Scan method: continuous
Specimen mounting: quartz capillary	2θmin = 10°, 2θmax = 109.983°, 2θstep = 0.027°
Data collection mode: transmission

Refinement

Rp = 0.007	23 restraints
Rwp = 0.010	7 constraints
Rexp = 0.004	All H-atom parameters refined
R(F) = 0.016	Weighting scheme based on measured s.u.'s w = 1/[σ^2(I) + 0.0016I^2]
3760 data points	(Δ/σ)max = 0.050
Profile function: pseudo-Voigt	Background function: 30 Legendre polynomials
71 parameters	Preferred orientation correction: none

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Na1	0	0	0.5	0.116 (12)*
Yb1	0.5	0.1430 (3)	0.75	0.042 (2)*
B1	0.5	0.263 (2)	0.963 (3)	0.049 (12)*
H1	0.5	0.320 (5)	0.064 (6)	0.058 (15)*
H2	0.5	0.172 (3)	1.002 (7)	0.058 (15)*
H3	0.6113 (2)	0.280 (4)	0.893 (4)	0.058 (15)*
B2	0.739 (3)	0.041 (2)	0.75	0.049 (12)*
H4	0.866 (5)	0.006 (8)	0.75	0.058 (15)*
H5	0.744 (12)	0.136 (2)	0.75	0.058 (15)*
H6	0.673 (5)	0.011 (4)	0.85368 (19)	0.058 (15)*

Geometric parameters (Å, º)

B1—H1^i	1.14 (6)	B2—H4	1.15 (6)
B1—H2	1.15 (5)	B2—H5	1.15 (4)
B1—H3	1.15 (3)	B2—H6	1.15 (3)
B1—H3^ii	1.15 (3)	B2—H6^iii	1.15 (3)
H1^i—B1—H2	109 (5)	H4—B2—H5	109 (7)
H1^i—B1—H3	110 (3)	H4—B2—H6	110 (3)
H1^i—B1—H3^ii	110 (3)	H4—B2—H6^iii	110 (3)
H2—B1—H3	110 (3)	H5—B2—H6	109 (4)
H2—B1—H3^ii	110 (3)	H5—B2—H6^iii	109 (4)
H3—B1—H3^ii	109 (3)	H6—B2—H6^iii	110 (3)

Symmetry codes: (i) x, y, z+1; (ii) −x+1, y, z; (iii) x, y, −z+3/2.